The present invention relates to a water-dispersible polymeric composition that can be used to prepare quick-set films or coatings.
Coatings provide protective barriers for a variety of things including floors, automobiles, exteriors and interiors of houses, and human skin. Protective coatings for floors, for example, have been known since the mid 1950s. Many of the early coating materials were applied using petroleum- or naphthene-based solvents and as such were undesirable due to the toxicity and flammability of these solvents.
Water-based synthetic emulsion compositions, such as styrene resin emulsions, styreneacrylate copolymer resin emulsions, and acrylate emulsions, developed in the early 1960s, gradually replaced organic solvent-based compositions. Although these water-based compositions are less toxic and more environmentally friendly than organic solvent-based compositions, the water-based compositions tend to be slow to set and difficult to remove in an application where removability is desired. Removal of coatings may be desirable because even the most durable coatings tend to deteriorate due to soiling or wear and tear. In other applications, such as protective care products for the skin, the advantages of water-based removable coatings are obvious.
Removable, water-based coatings are known. For example, polymers that contain ammonium carboxylate functionality are water compatible, but become incompatible through the loss of solvent and ammonia. ##STR1##
Coatings made by the above-illustrated process can be subsequently removed by contact with an aqueous alkaline liquid, which converts the acid back into the compatible salt.
For example, in U.S. Pat. No. 4,622,360, Gomi et al. discloses a removable water-borne polyurethane resin containing carboxyl groups. Coating compositions can be prepared by adding a polyvalent complex-forming metal to the water-borne resin. The polyvalent metal forms a stable water-dispersible complex with an amine or ammonia in the aqueous solution. When the dispersion is applied to a floor surface, noxious volatile materials evaporate to allow the polyvalent metal ions to initiate a crosslinking of two or more carboxyl groups, thereby forming a hardened, water-incompatible coating. This hardened coating can be removed, but only with a harsh alkaline solution containing ligands such as ethylene diamine tetraacetic acid.
The ammonium carboxylate coating suffers from several disadvantages: 1) the formulations are malodorous and irritating to the eyes and skin; 2) long set times are required to attain acceptable physical properties of the coating; and 3) the removal or stripping process requires the use of hazardous alkaline liquids.
In view of the deficiencies of the known art, it would be desirable to have a composition that provides a quick-set film or coating that can be removed without the use of harsh chemicals in applications where such removal is desirable. It would further be desirable to render such a coating resistant to common organic solvents in applications where general solvent resistance is desired.
It would further be useful to have a hypoallergenic, non-toxic, water-based composition that provides a coating that gives long-lasting protection to the skin against sun, dryness, and harsh chemicals.